\$\begingroup\$Historical note: The number of pages required for a spell has varied from edition to edition. In third edition, it was two pages per spell level and one page for cantrips; In 3.5rd edition, it was one page per spell level and one page per cantrip; In earlier editions, the number of pages required by the spell was the sum of the spell's level and a die roll...\$\endgroup\$
– GMJoeApr 18 '16 at 0:46

4 Answers
4

You're right that the 5e PHB does not mention how many pages are needed for spells, though as you point out spellbooks are given as having "100 blank vellum pages" (PHB 153).

The only hint that there might be a difference per spell level is in comparing these two texts from the "Your spellbook" sidebar on PHB 114:

For each level of the spell, the process takes 2 hours and costs 50 gp. The cost represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it.

(...)

You can copy a spell from your own spellbook into another book— for example, if you want to make a backup copy of your spellbook. This is just like copying a new spell into your spellbook, but faster and easier, since you understand your own notation and already know how to cast the spell. You need spend only 1 hour and 10 gp for each level of the copied spell.

We can deduce that the 10 gp cost for making backup copy is mostly the cost of ink, as you no longer need to expend material components for experimentation. As this amount is per spell level, it would suggest that higher level spells take up more ink, and therefore more space in the spellbook.

\$\begingroup\$I agree although we may be thinking that way because it has been that way in previous editions... The cost could be that the one page for that one spell is much more complicated and thus requires a lot more of that special ink.\$\endgroup\$
– Alexis WilkeFeb 22 '15 at 22:31

9

\$\begingroup\$You're right of course that more ink doesn't necessarily mean more pages, which is why I've worded my answer cautiously. Subjectively I wonder if things have been left deliberately vague in 5e, in a similar vein to the very relaxed and optional encumberance rules (PHB 176). I wonder if the new rules just keep the fun 'new spell tax' without getting bogged down in detailed bookkeeping.\$\endgroup\$
– harlandskiFeb 23 '15 at 0:20

I could find no explicit rulings on this within the released material.

pp 114 PHB for spellbook description particularly the section called The Book's Appearance in the bottom left corner.

Now I don't have any wizards in my current party but I'd DM it as being a magical collection of the characters known spells and let them decide from there.

Their decision hardly affects the game, maybe they prefer to keep all their spells written in chicken scratch on a notecard like a cheat sheet from school that they squint and read off. Or maybe its a massive tome with a whole entry for every spell including its history, origins and detailed uses throughout history.

\$\begingroup\$I could definitively see large tomes with quite complete spell history (or at least examples of use of the spell) in a library. But to carry around in your adventures, maybe not... 8-)\$\endgroup\$
– Alexis WilkeFeb 22 '15 at 21:30

No core mechanics in 5th edition in regards to page usage.
As mentioned above, the section of the PHB with your spellbook's information/appearance allows you to use anything that you could record information on, at the cost of 2hrs and 50gp (per level of spell) for new spells, and half as much for ones you already have prepared/recorded.

In the AL module 'The Visitor,' the antagonist's spellbook was a collection of brass plates/sheets, attached together by a large brass ring.
Your entire spellbook could be a gilt tome, a loose collection of notes, a leather volume, etc. The point is that you can make it as simple, flourished/flavorful as you like, as per the core mechanics.

If the DM wishes to put any additional costs to learning spell/skills, that's between them and their players to figure out. As far as Adventure's League goes, it is my understanding that you must use the information that is openly available as per the PHB/ errata for that edition. If it's not mentioned, then it has been excluded from that edition, (similar to what happened with paladins and monks between the different editions)

My personal ruling on the matter has always been and remains the same: each spell takes up a number of pages equal to its spell level.

There are two reasons I do this. First is simply that it's important to have a simple solution to a simple question — how many spells will fit in my spell book? The second reason is to create an economy in my game setting that includes the wizard. It's true that my wizards might fill up their spell books pretty quickly so it keeps my wizards participating in the market with buying spell books, attuning to a different book when they need to fill a different role. At 100G a pop, that's nothing for a high level wizard to afford. Third, now that the wizard is in the market for a new spellbook it gives me the opportunity as the DM to homebrew spellbooks with metamagic abilities worked into the pages. Example below: